Move animation out

src/animator.rs

+use specs::prelude::*;
+
+use crate::components::*;
+
+struct Animator;
+
+impl<'a> System<'a> for Animator {
+    type SystemData = (
+        WriteStorage<'a, MovementAnimation>,
+        WriteStorage<'a, Sprite>,
+        ReadStorage<'a, Velocity>,
+    );
+
+    fn run(&mut self, mut data: Self::SystemData) {
+        use self::Direction::*;
+
+        for (anim, sprite, vel) in (&mut data.0, &mut data.1, &data.2).join() {
+            if vel.speed == 0 {
+                continue;
+            }
+
+            let frames = match vel.direction {
+                Left => &anim.left_frames,
+                Right => &anim.right_frames,
+                Up => &anim.up_frames, 
+                Down => &anim.down_frames,
+            };
+
+            anim.current_frame = (anim.current_frame + 1) % frames.len();
+            *sprite = frames[anim.current_frame].clone();
+        }
+    }
+}

src/main.rs

 mod components;
 mod physics;
+mod animator;
 
 use sdl2::pixels::Color;
 use sdl2::event::Event;
         }
 
         i = (i + 1) % 255;
-        update_player(&mut player);
+        // TODO: Do with specs!
 
         render(&mut canvas, Color::RGB(i, 64, 255 - i), &texture, &player)?;